Harrell was a candidate for the club’s No. 1 spot during spring training and was the Astros’ best overall pitcher in 2012. This year, he’s alternately been one of the American League’s best and worst pitchers.

Harrell, 28, is 5-9 with a 5.04 ERA. He’s allowed one earned run or less in 10 of his 19 starts. But he gave up seven earned runs and walked six Friday during the Astros’ 10-5 loss to the Rangers and has allowed five earned runs or more in six outings.

Harrell’s demotion is much more similar to Jordan Lyles being cut from the big-league roster during spring training than Erik Bedard’s brief move to the bullpen.

“The overall answer to (his return) will come down to him. … Sometimes, we take a step backwards to take three steps forward,” Porter said. “And it all depends on how you take the news — (it) will go a long way in how you are able to get through this phase of your career.”

Harrell went 11-11 with a 3.76 ERA in 2012, striking out 140 and walking just 78 in 193 innings. This season, his strikeout-to-walk ratio has fallen to 1.26 (67 strikeouts, 53 walks) and he’s failed to reach the fifth inning in five starts.

“It’s a combination of wanting him to get back to the bullpen, get some things figured out,” Porter said. “This guy was one of our better pitchers last year. For whatever reason, there’s been a lot of inconsistency.”

Harrell was unapproachable for about 15 minutes in the Astros’ clubhouse following his recent loss to the Rangers. While his move to the bullpen is being made in the hope he can regain his 2012 form, it’s also being done to send a message to the mercurial pitcher, who’s blamed everything from the club’s defensive shifts to a lack of offense for his 2013 struggles.

“I’m trying to find time when (my season) was really good,” Harrell said Friday. “I haven’t been good all year. It’s been a pretty bad year and I haven’t thrown the ball well at all.”

The righthander has long been mentioned in trade rumors. Harrell would likely be a No. 4 or 5 starter on a winning team, though, and everything from his age and unproven career track record to his uneven 2013 season limit his value as the July 31 deadline approaches.

Following a Sunday series finale against the Rangers, the Astros will play five games in seven days before the All-Star break. Porter has yet to set the club’s rotation for a three-game series at Tampa Bay. The manager said a new fifth starter could be named and a short-term move — promoting a pitcher already on the 25-man roster from the bullpen — is an option. However, the Astros could simply use four starters until the break.

Bud Norris is scheduled to start Tuesday at St. Louis and Lyles will face the Cardinals on Wednesday. Brad Peacock and Jarred Cosart are among the candidates for promotion from Class AAA Oklahoma City. But the Astros also have starters turned relievers such as Paul Clemens, Brett Oberholtzer and Travis Blackley in their current bullpen.

“It all depends. As the next couple days go along, Jeff (Luhnow) and Doug (Brocail) and myself and the staff, we’ll talk about it and try to figure out what’s the best move,” Porter said. “It really is one start before we finish the first half of the season before we head into the All-Star break. And then we basically will go back to a five-man rotation in its earnest throughout the course of the regular season.”